Various mechanical seals have been provided for sealing radial spaces between a rotating shaft unit and an equipment body. Of these seals, segmented shaft seals have been provided which comprise a seal ring defined by arcuate ring segments that are retained within a holder in circumferentially adjacent relation to define an annular seal ring. The ring segments are biased radially inwardly by a spring into circumferential contact with the rotating shaft to define a circumferential seal about the outer surface of the shaft unit.
Some of such seals include cavities on the inner surfaces of the rings which receive fluid being sealed therein to generate an outward radial lifting force. An example of such a seal is disclosed in U.S. Pat. No. 3,874,677 (Ludwig, et al).
In known conventional seals, such seals often require machining on the inside diameter to form annular grooves or on the outside diameter to form an additional annular groove in which a garter spring is seated, which machining has proven to be undesirable. Further, such annular grooves such as these tend to collect contaminants and debris carried in the sealed fluid.
It is an object of the invention to overcome these and other disadvantages associated with such known segmented shaft seals.
The invention relates to an improved segmented shaft seal, which is particularly designed to facilitate molding of the shaft segments and eliminate machining thereof. In this regard, the ring segments of the invention are formed with tapered lift grooves on the inside diameter thereof which taper radially and/or circumferentially to permit axial removal of a mold die during molding of the ring segments. The tapered shape of the lift grooves further facilitates the formation of radial hydrostatic lift during operation of the seal so as to counteract radially inwardly directed spring forces generated by a garter spring extending about the ring segments and thereby reduce the contact pressure between the inner diameter of the seal ring and the opposing outer shaft surface.
Additionally, the ring segments are formed with a spring channel on the outside thereof which is open axially on one side so as to permit axial sliding of the garter spring onto the ring segments. The spring channel is configured so as to readily permit axial removal of a mold die such that molding forms the spring channel which eliminates the need for machining thereof.
Still further, the seal ring of the invention includes an improved assembly wherein the ring segments are seated within an annular cup-shaped housing and held in place along with a garter spring by a backing ring, which is frictionally fitted within an open side of the housing.
The segmented shaft seal of the invention provides advantages over prior art segmented seals in the formation of the ring segments, the assembly of the seal components and the operation of the seal.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.